Possibility of in vitro Alterations in Cultures of Mammary Carcinoma Cells, and Altered Immunological Response in the Rat: Acquired Capacity to Reject Injections of Mammary Carcinoma Cells and Implants of Mammary Carcinoma

Cell cultures derived from a mammary adenocarcinoma carried in inbred Fisher (CDF) strain female rats, have been shown to possess oncogenic activities and on injection into control rats to produce mammary carcinomata with a failure rate of only one out of 25 rats (i.e. 4%). Efforts have been made to alter the cultured cells, or to select populations from them, so that the response in rats to their antigenic characteristics might leave them with the ability to then reject injections of the active, untreated cancer cells. We have found that continuous treatment of the cultures by their own cell debris (sonicate), or by relatively high concentrations of intact, salmon-sperm DNA, lead to cell populations which have a decreased potential to produce mammary carcinomata, with a combined failure rate of 9 out of 12 rats (i.e. 75%): 5 out of these 12 rats (i.e. 41·7%) did not exhibit any growth (carcinomata or granulomata) after injection of these treated cells, and now all 5 (i.e. 100%) have the capacity to reject injections of the untreated, active cancer cells. Four of these rats (one died under anaesthesia) have now been found to also reject implants of the carcinoma itself.